Merge multiple Lists into one List with LINQ

Question

Is there a slick way to merge multiple Lists into a single List using LINQ to effectively replicate this?

public class RGB
{
    public int Red { get; set; }         


        

Answer 1

You can use Aggregate with Zip to zip an arbitrary number of IEnumerables in one go.

Here's how you might do that with your example:

var colorLists = new List[] { red, green, blue };
var rgbCount = red.Count;
var emptyTriples =
    Enumerable.Repeat>>(() => new List(), rgbCount)
    .Select(makeList => makeList());

var rgbTriples = colorLists.Aggregate(
    emptyTriples,
    (partialTriples, channelValues) =>
        partialTriples.Zip(
            channelValues,
            (partialTriple, channelValue) =>
            {
                partialTriple.Add(channelValue);
                return partialTriple;
            }));

var rgbObjects = rgbTriples.Select(
    triple => new RGB(triple[0], triple[1], triple[2]));

Generally, relying on Zip as the underlying combiner avoids problems with varying input lengths.